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1.  β2-Adrenergic Receptor Agonists Modulate Human Airway Smooth Muscle Cell Migration via Vasodilator-Stimulated Phosphoprotein 
Severe asthma manifests as airway remodeling and irreversible airway obstruction, in part because of the proliferation and migration of human airway smooth muscle (HASM) cells. We previously reported that cyclic adenosine monophosphate–mobilizing agents, including β2-adrenergic receptor (β2AR) agonists, which are mainstay of asthma therapy, and prostaglandin E2 (PGE2), inhibit the migration of HASM cells, although the mechanism for this migration remains unknown. Vasodilator-stimulated phosphoprotein (VASP), an anticapping protein, modulates the formation of actin stress fibers during cell motility, and is negatively regulated by protein kinase A (PKA)–specific inhibitory phosphorylation at serine 157 (Ser157). Here, we show that treatment with β2AR agonists and PGE2 induces the PKA-dependent phosphorylation of VASP and inhibits the migration of HASM cells. The stable expression of PKA inhibitory peptide and the small interfering (si) RNA-induced depletion of VASP abolish the inhibitory effects of albuterol and PGE2 on the migration of HASM cells. Importantly, prolonged treatment with albuterol prevents the agonist-induced phosphorylation of VASP at Ser157, and reverses the inhibitory effects of albuterol and formoterol, but not PGE2, on the basal and PDGF-induced migration of HASM cells. Collectively, our data demonstrate that β2AR agonists selectively inhibit the migration of HASM cells via a β2AR/PKA/VASP signaling pathway, and that prolonged treatment with albuterol abolishes the inhibitory effect of β-agonists on the phosphorylation of VASP and migration of HASM cells because of β2AR desensitization.
PMCID: PMC3262659  PMID: 22210825
airway hyperresponsiveness; β2-adrenergic receptor desensitization; protein kinase A; albuterol; formoterol
2.  Expression and activation of the oxytocin receptor in airway smooth muscle cells: Regulation by TNFα and IL-13 
Respiratory Research  2010;11(1):104.
During pregnancy asthma may remain stable, improve or worsen. The factors underlying the deleterious effect of pregnancy on asthma remain unknown. Oxytocin is a neurohypophyseal protein that regulates a number of central and peripheral responses such as uterine contractions and milk ejection. Additional evidence suggests that oxytocin regulates inflammatory processes in other tissues given the ubiquitous expression of the oxytocin receptor. The purpose of this study was to define the role of oxytocin in modulating human airway smooth muscle (HASMCs) function in the presence and absence of IL-13 and TNFα, cytokines known to be important in asthma.
Expression of oxytocin receptor in cultured HASMCs was performed by real time PCR and flow cytomery assays. Responses to oxytocin was assessed by fluorimetry to detect calcium signals while isolated tracheal rings and precision cut lung slices (PCLS) were used to measure contractile responses. Finally, ELISA was used to compare oxytocin levels in the bronchoalveloar lavage (BAL) samples from healthy subjects and those with asthma.
PCR analysis demonstrates that OXTR is expressed in HASMCs under basal conditions and that both interleukin (IL)-13 and tumor necrosis factor (TNFα) stimulate a time-dependent increase in OXTR expression at 6 and 18 hr. Additionally, oxytocin increases cytosolic calcium levels in fura-2-loaded HASMCs that were enhanced in cells treated for 24 hr with IL-13. Interestingly, TNFα had little effect on oxytocin-induced calcium response despite increasing receptor expression. Using isolated murine tracheal rings and PCLS, oxytocin also promoted force generation and airway narrowing. Further, oxytocin levels are detectable in bronchoalveolar lavage (BAL) fluid derived from healthy subjects as well as from those with asthma.
Taken together, we show that cytokines modulate the expression of functional oxytocin receptors in HASMCs suggesting a potential role for inflammation-induced changes in oxytocin receptor signaling in the regulation of airway hyper-responsiveness in asthma.
PMCID: PMC2922094  PMID: 20670427
3.  Expression and Role of the Hyaluronan Receptor RHAMM in Inflammation after Bleomycin Injury 
Lung injury is associated with increased concentrations of hyaluronan (hyaluronic acid, HA). HA modifies cell behavior through interaction with cell-associated receptors such as receptor for HA-mediated motility (RHAMM, CD168). Using a function blocking anti-RHAMM antibody (R36), we investigated the expression and role of RHAMM in the inflammatory response to intratracheal bleomycin in rats. Immunostaining showed increased expression of RHAMM in macrophages 4–7 d after injury. Surface biotin labeling of cells isolated by lavage confirmed increased surface expression of a 70-kD RHAMM after lung injury, and in situ hybridization demonstrated increased RHAMM mRNA in macrophages responding to injury. Time-lapse cinemicrography demonstrated a 5-fold increase in motility of alveolar macrophages from bleomycin-treated animals that was completely blocked by R36 in vitro. Further, HA-stimulated macrophage chemotaxis was also inhibited by R36. Daily administration of R36 to injured animals resulted in a 40% decrease in macrophage accumulation 7 d after injury. Further, H&E staining of tissue sections showed that bleomycin-mediated changes in lung architecture were improved with R36 treatment. Taken together with previous results showing the inhibitory effects of HA-binding peptide on inflammation and fibrosis, we conclude that the interaction of RHAMM with HA is a critical component of the recruitment of inflammatory cells to the lung after injury.
PMCID: PMC2715352  PMID: 16037485
lung injury; bleomycin; inflammation; hyaluronan; RHAMM
4.  Hormonal regulation of alveolarization: structure-function correlation 
Respiratory Research  2006;7(1):47.
Dexamethasone (Dex) limits and all-trans-retinoic acid (RA) promotes alveolarization. While structural changes resulting from such hormonal exposures are known, their functional consequences are unclear.
Neonatal rats were treated with Dex and/or RA during the first two weeks of life or were given RA after previous exposure to Dex. Morphology was assessed by light microscopy and radial alveolar counts. Function was evaluated by plethysmography at d13, pressure volume curves at d30, and exercise swim testing and arterial blood gases at both d15 and d30.
Dex-treated animals had simplified lung architecture without secondary septation. Animals given RA alone had smaller, more numerous alveoli. Concomitant treatment with Dex + RA prevented the Dex-induced changes in septation. While the results of exposure to Dex + RA were sustained, the effects of RA alone were reversed two weeks after treatment was stopped. At d13, Dex-treated animals had increased lung volume, respiratory rate, tidal volume, and minute ventilation. On d15, both RA- and Dex-treated animals had hypercarbia and low arterial pH. By d30, the RA-treated animals resolved this respiratory acidosis, but Dex-treated animals continued to demonstrate blood gas and lung volume abnormalities. Concomitant RA treatment improved respiratory acidosis, but failed to normalize Dex-induced changes in pulmonary function and lung volumes. No differences in exercise tolerance were noted at either d15 or d30. RA treatment after the period of alveolarization also corrected the effects of earlier Dex exposure, but the structural changes due to RA alone were again lost two weeks after treatment.
We conclude that both RA- and corticosteroid-treatments are associated with respiratory acidosis at d15. While RA alone-induced changes in structure andrespiratory function are reversed, Dex-treated animals continue to demonstrate increased respiratory rate, minute ventilation, tidal and total lung volumes at d30. Concomitant treatment with Dex + RA prevents decreased septation induced by Dex alone and results in correction of hypercarbia. However, these animals continue to have abnormal pulmonary function and lung volumes. Increased septation as a result of RA treatment alone is reversed upon discontinuation of treatment. These data suggest that Dex + RA treatment results in improved gas exchange likely secondary to normalized septation.
PMCID: PMC1448204  PMID: 16566837

Results 1-4 (4)